Germanium (Ge) channels or high germanium content silicon germanium (SiGe) channels have been studied to improve device performances. However, germanium layers or high germanium content silicon germanium layers formed on a silicon substrate may include various defects due to lattice mismatches between the silicon substrate and the germanium layers or high germanium content silicon germanium layers and may thus increase undesired leakage.
A germanium condensation process using an oxidation process has been proposed to reduce defects due to lattice mismatches between a silicon substrate and germanium layers or high germanium content silicon germanium layers. However, the germanium condensation process may result in strain built in germanium layers or high germanium content silicon germanium layers and may cause extended defects.